低气压微波感耦氩等离子体空间分布特性光谱诊断

用二维光学多道分析仪研究了低气压表面波型微波感耦氬等离子体的光谱辐射特性?鼳bel反演后,得到了在各种气压和微波功率下等离子体辐射光强和激发温度的空间分布及其变化规律。讨论了此等离子体的激发机理。     

环境气氛对高能量激光诱导等离子体辐射特性的影响

采用高能量钕玻璃激光器(～25 J)激发诱导金属等离子体,研究了环境气体及其压力对等离子体辐射特性的影响。实验结果表明,相同压强下,氩气中等离子体的谱线强度明显高于空气中等离子体的谱线强度;0.8×105Pa氩气条件下,光谱标钢等离子体的谱线强度达到了最大值;随着环境气压的增大,谱线自吸明显增强,当环境气压达到(0.8～0.93)×105Pa时,标样铝的AlⅠ308.22 nm和AlⅠ309.27 nm两条谱线产生了严重自蚀;另外,等离子体的激发温度也随环境气压的增大而增大,0.93×105Pa氩气条件下标钢等离子体的激发温度相对于0.43×105Pa时升高了近1 500 K。     

透镜与样品之间距离对激光等离子体辐射特性的影响

采用高能量钕玻璃激光器产生的激光(～25J)在减压氩气环境下诱导钢和土壤样品等离子体,研究了激光束聚焦透镜(f=130 mm)与样品之间距离对等离子体辐射特性的影响。实验结果表明,当聚焦透镜的焦点围绕样品表面上下移动时,对于合金钢样品,激光束焦斑位于样品表面以下0.4 mm左右,则激光等离子体的辐射强度、激发温度和物质烧蚀质量均出现最大值;而对于土壤样品,当激光束聚焦位置在样品表面以下0.2 mm左右,等离子体辐射强度和物质烧蚀质量具有最大值。为了比较透镜与样品之间距离对等离子体形状的影响,也拍摄了氩气和空气环境下产生的激光等离子体象。所得结果证明,激光等离子体特性明显依赖于透镜与样品之间距离。     

Excitation of Doubly‐Charged Ion Emission Lines from a Grimm‐Style Glow Discharge Plasma—Comparison Between Yttrium and Zirconium

Spectra of yttrium and zirconium emitted from a Grimm‐style glow discharge plasma were investigated to elucidate the excitation mechanism of doubly‐charged ionic lines when using argon–helium mixed gas as well as argon gas alone. The energy sum for exciting doubly‐charged ion species of yttrium is slightly smaller compared to the case of zirconium, which yields an interesting correlation in the excitation energy between their ionic species and excited species of helium or argon. The Y III emission lines which were assigned to the 4p⁶5p–4p⁶5s(4p⁶4d) transitions could be observed in the argon–helium mixed gas plasma, but those were hardly excited with argon gas only. The Zr III emission lines did not appear in the spectra emitted by the argon gas plasma nor by the mixed gas plasma. A possible explanation for these phenomena is that the excitation of these ionic species is caused principally by collisional energy transfer from helium species to the analyte atoms.     

Comparative Study on Excitation Mechanism of Chromium Emission Lines in Argon Radio‐Frequency Inductively‐Coupled Plasma,Nitrogen Microwave Induced Plasma,and Argon or Nitrogen Glow Discharge Plasmas

Boltzmann plots of both atomic and ionic chromium emission lines are investigated to compare the excitation mechanisms in four different plasmas: an argon inductively‐coupled plasma (Ar‐ICP), a nitrogen high‐power microwave induced plasma (N₂‐MIP), an argon glow discharge plasma (Ar‐GDP), and a nitrogen glow discharge plasma (N₂‐GDP). The plots of the atomic lines and the ionic lines give both linear relationships as well as similar excitation temperatures in the case of the Ar‐ICP, the N₂‐MIP, and the N₂‐GDP. It implies that a thermodynamic process such as electron collision would control their excitations. However, only in the case of the ionic‐line plot in the Ar‐GDP, a departure from linear relationship is observed and the estimated excitation temperature is rather higher than that with the atomic lines, meaning that a specific excitation mechanism exists in the Ar‐GDP. A possible explanation for these results is that a charge‐transfer collision between chromium atom and argon ion plays a dominant role in exciting highly‐lying energy levels of chromium ion, especially in the Ar‐GDP.     

Studies on wettability of medical poly(vinyl chloride) by remote argon plasma

The paper studies surface modification of medical poly(vinyl chloride) (PVC) by remote argon plasma and characterized surface structure, performance of treated PVC by the water contact angle measurement, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Results show that the remote argon plasma makes the surface of the PVC film higher hydrophilic than the direct argon plasma and does not give remarkable degradation on the PVC film surface. The hydrophilicity depends on sample position as well as the RF power and the plasma exposure time. The remote argon plasma contributes more effectively to the dechlorination (Cl/C = 0.01) from the PVC film than the direct argon plasmas (Cl/C = 0.03) and more effectively to the formation oxygen functionalities on the PVC film surface. These experimental results show the possibility that remote argon plasma treatment can enhance interaction reactions with argon radicals relative to those with electron and argon ions.     

Surface modification of polypropylene using argon plasma: Statistical optimization of the process variables

Low pressure plasma treatment using radiofrequency (rf) discharge of argon gas was employed to improve the hydrophilicity of polypropylene. The effects of argon plasma on the wettability, surface chemistry and surface morphology of polypropylene were studied using static contact angle measurements, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Increase in surface energy of polypropylene was observed as a result of argon plasma treatment. SEM and AFM images revealed the increased surface roughness. A set of identified process variables (rf power, pressure, argon flow rate and time) were used in this study and were optimized using central composite design (CCD) of response surface methodology (RSM). A statistical model was developed to represent the surface energy in terms of the process variables mentioned above. Accuracy of the model was verified and found to be high.     

Surface properties of platinum thin films as a function of plasma treatment conditions

We examined the surface properties of platinum (Pt) thin films exposed to oxygen and argon plasma treatments and compared them to as-deposited Pt films. The surface wetting properties, refractive index and extinction coefficient of the Pt films were monitored as a function of time after different plasma treatments. Surfaces treated with an oxygen plasma were dramatically different from as-deposited Pt, whereas argon plasma treated surfaces were similar to as-deposited films. X-ray photoelectron spectroscopy confirmed the formation of platinum oxide on films treated with an oxygen plasma, while such oxide diminished after argon plasma treatment. Surface morphology studied with atomic force microscopy indicated a strong dependence of the surface roughness of the Pt films on the power and duration of the argon plasma used for the treatment. Based on these studies, an oxygen plasma treatment followed by a brief low-power argon plasma etch was developed for the purpose of regenerating clean and metallic Pt surfaces, and at the same time providing the smoothest possible surface morphology.     

Measurement of neutral gas temperature in inductively coupled plasmas

Dependence of the neutral gas temperature on the gas pressure and discharge power in an inductively coupled plasma source has been investigated using optical emission spectroscopy. Both nitrogen and argon plasmas have been studied separately. In the case of argon plasma, about 5% nitrogen was added to the total gas flow as an actinometer. The maximum temperature was found to be as high as 1850 K at 1 Torr working pressure and 600 W radiofrequency power. The temperature increases almost linearly with the logarithm of the gas pressure, but changes only slightly with the discharge power in the range of 100–600 W. In a nitrogen plasma, a sudden increase in the neutral gas temperature occurs when the gas pressure is increased at a given discharge power. This suggests a discharge-mode transition from the H-mode (high plasma density) to the E-mode (low plasma density). In the H-mode, the gas temperature is proportional to the logarithm of the gas pressure, as in the argon plasma. However, the gas temperature increases almost linearly with the discharge power, which is in contrast to the case of argon plasma. The electron density in the nitrogen plasma is about 10% of that in the argon plasma. This may explain the observation that the nitrogen neutral temperature is always lower than the argon neutral temperature under the same discharge power and gas pressure.     

大气压直流氩等离子体光谱诊断研究

通过光谱诊断系统测量了大气压直流氩等离子体射流在弧室内和弧室出口的发射光谱,利用波尔兹曼曲线斜率法计算了射流的电子温度,根据Ar Ⅰ谱线的斯塔克展宽得到射流的电子密度,并对氩等离子体射流满足局域热力学平衡(LTE)状态的判定标准进行了分析,结果表明在文章的实验条件下大气压直流氩等离子体射流达到局域热力学平衡。